Perfluoropolyether acylperoxides and process for their preparation

ABSTRACT

Perfluoroether acylperoxides having an average equivalent weight in the range of 350-5000, and of the following formulae: 
     
       
         Y′—(CF 2 —CF(CF 3 )O) m —(CX′FO) n —CF 2 CO—O—O—CO—CF 2 —(OCX′F) n —(OCF(CF 3 )—CF 2 )—Y′  (I) 
       
     
     wherein 
     Y′=Cl, OR f  wherein R f  is a C 1 -C 3  perfluoroalkyl; 
     m, n are integers such that the average equivalent weight of (I) is in the range of 350-5000 and m/n≧40; 
     X′=F, CF 3 ; 
     
       
         T—CF 2 —O—[(CF 2 CF 2 O) p —(CF 2 O) q —CF 2 —CO—O—O—CO—CF 2 (OCF 2 ) q —(OCF 2 CF 2 ) p ] y —OCF 2 —COOH  (II) 
       
     
     wherein 
     y is an integer comprised between 1 and 5; 
     p and q are integers such as to give the above mentioned EW and p/q=0.5 to 2.0; 
     T=COOH, F with the proviso that when T=COOH 
     y=1-5, when T=F then y=1, and processes for manufacturing them.

The present invention relates to an improved process to obtain with highyields poly- and diacyl-peroxides of (per)-fluoropolyethers startingfrom the corresponding diacyl- and monoacyl-halides.

Perfluoroether diacylperoxide syntheses have already been described inthe art.

H. Sawada in Reviews of Heteroatom Chemistry Vol. 8, pages 205-231mentions a perfluoro-oxa-alkanoyl peroxides series of formula(R_(fa)CO₂)₂, wherein R_(fa)=C₃F₇O[CF(CF₃)CF₂O]_(m)CF(CF₃) and m=0, 1,2, 3, and reports that the behaviour to thermal decomposition and theiruses are known. Specifically it is reported that the synthesis takesplace in aqueous alkales in the presence of hydrogen peroxide. Noindication is given how the reaction is carried out.

WO 97/08142 describes a process to obtain diacylperoxides starting fromhalogen derivatives of formula R(C═O)X wherein X=halogen and R can be inparticular the following perfluoropolyether group:

G(CF₂)_(w1)[CF(CF₃)CF₂]_(x1)[OCF(CF₃)CF₂]_(y1)[OCF(CF₃)]_(z1)−

wherein w1, x1, y1, z1 are integers, w1 ranges from 0 to 8, x1 from 0 to1, y1 from 0 to 7, z1 from 0 to 1, w1+x1+y1+z1≧1, and G is fluorine or asubstituted carbon atom. The reaction, which can be carried out in batchor in a continuous way in a stable peroxide dispersion in KOH/H₂O₂ whichcontains the acylic halide, occurs in very short times, from few secondsto 30 seconds, under stirring such that the Reynolds number results inthe range 1.000-40.000. Fluorinated and non fluorinated organic solventsand surfactants can be added. The examples relate to the synthesis ofthe perf luoroether diacylperoxide having a low molecular weight fromHFPO having the formula [CF₃CF₂CF₂OCF(CF₃) (C═O)O]₂ (equivalent weight332), starting from the corresponding acylfluoride. The reactions aregenerally carried out at 0° C. but also at room temperature. The contacttime generally ranges, as said, from 1 to 30 seconds. The patentapplication reports also the peroxide synthesis starting from thefollowing acylfluoride having the formula

CF₃CF₂CF₂O[CF(CF₃)CF₂O]_(6,3)CF(CF₃)(C═O)F

having molecular weight of about 1300. The yield is 62%. Moreover, theprocess uses solvents having high ODP (e.g. CFCH₃, CF₂Cl—CFCl₂).

An object of the present invention is a process to obtain with improvedyields (per)fluoroether acylperoxides having an average equivalentweight (EW) in the range 350-5.000, having formula:

Y′—(CF₂—CF(CF₃)O)_(m)—(CX′FO)_(n)—CF₂CO—O—O—CO—CF₂—(OCX′F)_(n)—(OCF(CF₃)—CF2)_(m)—Y′  (I)

wherein

Y′=Cl, OR_(f) wherein R_(f) is a C₁-C₃ perfluoroalkyl;

m, n are integers such that (I) gives the mentioned EW and m/n≧40;

X′=F, CF₃;

T—CF₂—O—[(CF₂CF₂O)_(p)—(CF₂O)_(q)—CF₂—CO—O—O—CO—CF₂(OCF₂)_(q)—(OCF₂CF₂)_(p)]_(y)—OCF₂—COOH  (II)

wherein

y is an integer comprised between 1 and 5;

p and q are integers such as to give the above mentioned EW andp/q=0.5-2.0;

T=COOH, F with the proviso that if T=COOH y=1-5, if

T=F then y=1;

starting from perfluoroether acylhalides having an average molecularweight (MW) by number in the range 350-5.000, having, respectively, theformula:

Y′—(CF₂—CF(CF₃)O)_(m)—(CX′FO)_(n)—CF₂CO—Y″  (I′)

wherein

Y′, X′, m and n have the meaning indicated in

Y″=Cl, F;  (I);

Y′″—CF₂—O—(CF₂CF₂O)_(p)—(CF₂O)_(q)—CF₂—CO—Y″  (II′)

wherein

Y″ has the meaning indicated in (I′);

Y′″=CO—Y″, F;

by reaction with H₂O₂ in basic ambient.

The process is carried out at a temperature comprised between −5° C. and+5° C. in a mixture formed by two immiscible liquid phases having atotal volume equal to at most ⅔ of the reactor one, kept under stirringso that no emulsions are formed, said liquid phases being the following:

an organic phase formed by a polyhalogenated solvent having very lowODP, in an higher amount,

an aqueous alkaline solution containing an excess of hydrogen peroxidewith respect to the halide which is added;

said process comprising the following steps:

a) addition of a (per)fluoropolyether monoacyl or diacyl-halide bycooling so that the ΔT thermal increase, with reference to a reactorhaving an internal volume in the range 50-250 ml cooled by a 2 l volumecryogenic bath having a temperature comprised between −40° C. and −80°C., is in the range 6° C.-20° C. and that when the addition is over, thetemperature decreases to the initial one in a time comprised between 0.1and 5 minutes;

b) reacting, at the initial temperature, for the necessary time(t_(max)) to obtain the conversion of 75% of the acylhalide (I′), (II′),determined by quantitative FTIR analysis

c) reaction interruption, by stopping stirring and allowing the phasesto be separated by maintaining the system at the initial temperature,and recovery of the organic phase containing the perf luoropolyetherdiacyl-/polyacyl-peroxides.

Preferably in step a) the ratio between the alkali moles and the —CO—Y″functional groups equivalents is comprised between 1.2 and 1.8 and theratio between the aqueous phase ml volume and the base grams iscomprised between 5 and 10; preferably the organic phase volume is halfthan that of the reactor.

In order to obtain the thermal increases indicated in a), the reactantaddition is carried out in a time depending on the perfluoropolyetheracylic halides of formula (I′) and (II′) MW and it ranges from 20 to 30seconds for the perfluoropolyether acyclic halides having MW in therange 350-800 and it is lower than or equal to 15 seconds for thosehaving a MW in the range 800-5.000.

The polyhalogenated organic solvent is preferably (per)-fluorinated andis preferably selected from C₆-C₁₀ linear chain perfluoroalkanes,perfluoropolyethers having perfluoroalkylic end groups, optionallycontaining at one or both end groups an hydrogen atom, saidperfluoropolyethers having a low number average molecular weight,preferably in the range 400-1.000. The preferred solvents areperfluoropolyethers having perfluoroalkylic end groups.

The process object of the present invention is feasible both in batchand in a continuous way, and allows to obtain with high yieldspoly-acylperoxide or diacylperoxide mixtures with EW in the range350-5.000. Preferably peroxides of formula (II) with equivalent weights(EW) between 1.000 and 2.000, starting from (per)fluoropolyether halidesof formula (II′) with number average molecular weight 1.000-2.000, areobtained. Preferably diacylperoxides of formula (I) having preferablyequivalent weight in the range 350-800 starting from halides of formula(I′) with number average molecular weight 350-800, are obtained.

In the reaction product mixtures obtainable starting from (II′) therelative amounts of diacyl peroxides and polyacylproxides are related tothe hydrogen peroxide excess and, the conditions being equal, with thecompound (II′) molecular weight.

By using halides of formula (II′) with MW in the range 3.000-5.000,diacylperoxides of formula (II) with y=1 are obtained; by using halidesof formula (II′) with number average molecular weights in the range350-3.000, dipolyacylperoxides are obtained and in the formula (II)y=1-5 and T=COOH.

With average equivalent weight of the peroxide according to the presentinvention it is meant the equivalent weight calculated from themolecular weight of the starting acylhalide, subtracted the halogenatomic weight and added that of the oxygen.

The reaction yield is calculated by determining the titre in peroxidesof the organic phase by titration with an aqueous titrated solution ofsodium thiosulphate in the presence of a 50% w/v potassium iodideaqueous solution.

The (per)fluoropolyether peroxidation reaction yields according to thepresent invention depend on the parameters indicated in the inventionprocess steps:

the reaction exothermy control to maintain the mixture temperaturewithin the indicated range range. Tests carried out by the Applicanthave shown that the yields decrease when the thermal increases are notin the above specified limits;

the time (t_(max)) which elapses between the moment when the temperatureinside the system returns to the initial one and the moment whenstirring is stopped.

The total reaction time is determined from time to time by determiningthe acylhalide conversion percentage, which is obtained taking samplesfrom the reaction mixture at different times, starting when the additionof the (per)fluoropolyether monoacyl or diacyl-halide of formula (I′) or(II′), respectively, begins. More specifically the analysis is carriedout by the quantitative FTIR technique, by monitoring the peak areadecrease corresponding to the stretching of the compound of formula (I′)or (II′) acylic groups and determining the ratio with respect to theinitial area, the compound weight being the same. The reaction isstopped when this ratio reaches the required value (75% conversion of(I′) or (II′) at t_(max)).

It has been verified that by determining the peroxides concentration inthe reaction mixture by titration as indicated above, the reaction timecannot be determined. The concentration of these compounds reaches amaximum after few ten seconds from the reaction beginning and it keepsconstant for several minutes. FTIR analyses carried out on samples takenin correspondence of the reaction plateau have shown that the formedperoxide quickly hydrolyzes to carboxylic acid. This compound is alsoobtained, contemporaneously, by the direct acylhalide hydrolysis. Thefactor influencing the reaction yields is therefore the acylhalideamount which can still react. It has been verified that the best yieldsare obtained by stopping the reaction at the 75% of the acylhalideconversion.

It is possible to determine by ¹⁹F NMR analysis if in the organic phasecontaining the reaction products, diacylperoxides or polyacylperoxideshave been formed, after removing part of the solvent, so as toconcentrate the peroxidic fraction. The areas (A₁) of the peakscorresponding to the —CF₂— groups in alpha position to the end groups(e.g. —CF₂—COOH) and those (A₂) of the —CF₂— groups which are in alphawith respect to the peroxidic group [—CF₂—C(O)—O—O—C(O)—CF₂]_(n), aremeasured. The A₂/A₁ ratio allows an evaluation of the y value andtherefore to determine if the compound is a diacyl- or apolyacylperoxide.

The invention process gives particularly high yields for the peroxidesobtained from acylhalides (II′) having number average molecular weightin the range 1.000-2.000.

The Applicant has unexpectedly found that starting from acylhalideshaving number average molecular weight in the range 350-3.000, theinvention process allows to obtain with improved yields products whereinpolyacylperoxides are in a higher concentration.

The invention process has been found applicable also to averagemolecular weights of the starting compounds higher than 2.000, up to5.000, and the yields are industrially good and better than theprocesses of the art.

A further object of the invention consists in dipolyacylperoxides offormula (I) and (II).

The (per)fluorinated peroxides obtained by the process according to thepresent invention are used as chain initiators in (per)fluoroelastomerand thermoplastic polymerizations. These (per) fluorinated peroxideshave chemical physical properties such as to result compatible with thepolymerization system. Moreover the possibility to determine thehalf-life times of the peroxide homolitic decomposition on the basis ofits equivalent weight allows to select the most suitable operatingconditions for the polymerization.

The (per)fluoropolyether (di/poly)acyl peroxides can be used also asmodifiers of non fluorinated polymers, such as polyacrylates, to givebetter surface properties, or as intermediates for agrochemical andpharmaceutical compounds.

The following examples are given only for illustrative purposes of thepresent invention without limiting it.

EXAMPLE 1 Synthesis of a diacyl- and polvacyl-peroxides Mixture HavingStructure (II) (Z-PFPE) EW 1355.

The used equipment consists in a 200 ml glass flask having 4 groundnecks equipped with nechanical blade stirrer, condenser, dropping funneland thermometer. The equipment is assembled so that the flask can bedipped in a 2 l refrigerant bath and at a temperature between −40° C.and −70° C.

In the flask, at room temperature, 87.3 mmoles of finely milled NaOH in23.5 ml of distilled H₂O (equivalent to 6.75 ml H₂O/g NaOH) aredissolved; to this solution 35 mmoles of H₂O₂ at 57.5% w/w and 100 ml ofperfluorohexane C₆F₁₄ are added. The solution is cooled at 0° C. understirring (1512 rpm). In 15 seconds 29.1 mmoles of perfluoroetherdiacylchloride Z-PFPE of formula (II′) wherein p/q=0.5-2 MW 1374, aredropped. By dipping the reactor in a bath at −40° C. the reactionmixture exothermy does not exceed 9° C. When the exothermy is ended, thetemperature returns to 0° C. in 1.5 minutes. Stirring is continued at 0°C. for a time t_(max)=1 minute so as to obtain 75% of conversion(determined by FTIR analysis, peak at 1804 cm⁻¹) of the acylchloride. Atthis point stirring is stopped and the flask content is poured in aseparatory funnel, previously cooled at 0° C. After separation of thephases the organic phase is recovered, which is anhydrified by sodiumsulphate and filtered in a “Sartorius” pressure filter equipped onlywith prefilter. 167 g (density=1.72 g/ml) of clear organic solutionhaving a peroxide titre of 0.28 g peroxide/ml solution, equivalent to27.5 g of acyl peroxide having a calculated average EW 1355. The yield,calculated by the equivalent weight is 70%.

The t_(max) influence on the acyl peroxide yield is shown in Table 1.

EXAMPLES 2-3 (comparative) Synthesis of a diacyl- and polvacyl-peroxidesMixture Z-PFPE MW 1355 in Different Solvents

One proceeds as in Example 1. The addition time was 15 seconds while thet_(max) was fixed at the time when the acylchloride conversion was 75%.In Example 2 a perfluoropolyether (PFPE) having MW 800 is used as asolvent. In the comparative Example 3 the solvent is Freon® 113 (highODP).

Example Solvent Yield No. 2 PFPE MW 800 73% No. 3 Freon ® 113 55%

EXAMPLES 4-5 (comparative) Influence of the Addition Time on the Yieldsof the Obtained di-polvacylperoxide Product with EW 1355

Example 1 was repeated carrying out the reactant addition in a totaltime over the 20 seconds limit: 25 seconds in Example 4 and 300 secondsin Example 5.

Addition time Comparative acylchloride example (seconds) Yield No. 4 2532% No. 5 300  6%

In Example 4 the yields are 46% of those of Example 1, in Example 5about 9%.

EXAMPLE 6 Synthesis of a polyacyl-peroxides Mixture Z-PFPE EW 529 andDetermination of the Molecular Weight of the Obtained Product

The same equipment of Example 2 is used. 218.7 mmoles of NaOH dissolvedin 59.1 ml of water are introduced. 87.5 mmoles of H₂O₂ at 57.5% and 100ml of C₆F₁₄ are added to the solution. 72.9 mmoles of perfluoroetherdiacyl chloride Z-PFPE having MW=548.8, are dropped in the reactionmixture in 25 seconds. The reaction exothermy is controlled so that thetemperature rise in the mixture is of +11° C. The t_(max) is of 3.3 min.at 0° C. The mass is worked as described in Example 2. A product havinga calculated average EW 529 is obtained. The compound containspolyacylperoxides (Ex. 1).The peroxide yield is 72%.

The y parameter value in formula (II), and therefore the compoundequivalent weight, was determined as follows.

The poly-acylperoxide halflife (t_(½)) was determined with the followingmethod. 16-17 g of the peroxide were dissolved in 150 ml of C₆F₁₄. 1.5ml portions of this solution are distributed in test-tubes, which arethen closed and thermostated at 20° C. Starting from the zero time(experiment beginning), and then at regular intervals, the peroxidequantitative determination is carried out by titration withthiosulphate, by using 5-6 different samples at a time and calculatingan average value of the obtained titres. Then a graph is drawn,reporting in ordinates the solution concentration in g of peroxide/ml ofsolvent and in abscissas the time, expressed in minutes. In this way thet_(½) at 20° C. has been determined, which resulted of 4606 minutes.

The compound taken as a reference is a diacylperoxide having thestructure (I) wherein Y′=OCF₃ PE=1580, prepared from the correspondingperfluoroether monoacylchloride (I′) according to the process of Example2. The t_(½) value determined with the above mentioned method was of4500 minutes.

The substantial equality of the two peroxides t_(½) means that themolecular weight of the polyacylperoxide with PE 529 is very close tothat of the diacyl peroxide taken as a reference. i.e. 3160. Thereforethey parameter in the formula of the compound (II) has a value in therange 1-5. This shows that the obtained peroxide is a polyacylperoxide.

EXAMPLES 7-9 (comparative) Effect of the Thermal Rise on the ReactionYields

Example 6 was repeated changing the cooling system to allow AT thermalrises respectively below and over the +6-+20° C. limits. The ΔT valueswere respectively 3° C., 26° C., 32° C. (initial temperature 0° C.). Thefollowing comparative Examples 7-9 show that the previously mentionedthermal increase give rise to an yield decrease.

Comparative Thermal rise Example (° C.) Yield No. 7 +3 35% No. 8 +2640.2%   No. 9 +32 35%

In particular from Example 7 it results that by cooling the system inreaction so that the temperature rise is of 5° C., the yields are halfthan those of Example 6.

EXAMPLE 10 Synthesis of a polyacyl-peroxides Mixture Z-PFPE with EW 2204

The same equipment of Example 1 is used. 54 mmoles of NaOH dissolved in59.1 ml of water are introduced in the flask. 21.6 mmoles of H₂O₂ at57.5% and 80 ml of a C₆F₁₄-C₁₀F₂₂ mixture are added to the solution. 18mmoles of perfluoroether diacyl chloride Z-PFPE having MW=2223, aredropped in the reaction mixture in 15 seconds. The reaction exothermy iscontrolled so that the temperature rise in the reaction mixture does notexceed +10° C. The t_(max) results to be 3.5 min. at 0° C. The organicphase is recovered as described in Example 2. The peroxide yield is 71%.

EXAMPLE 11 Synthesis of diacyl-peroxide Z-PFPE with EW 4550

The equipment of Example 2 is used. 19.7 mmoles of NaOH dissolved in 5.3ml of water are introduced in the flask. 7.88 mmoles of H₂O₂ at 57.5%and 60 ml of a C₆F₁₄ are added to the solution. 6.57 mmoles ofperfluoroether diacyl chloride Z-PFPE having MW=4569, are dropped in thereaction mixture in 15 seconds. The reaction exothermy is controlled sothat the temperature rise in the mixture is of +9° C. The t_(max) is of6 min. at 0° C. The organic phase is recovered as described in Example2. 2 g of product are obtained, EW calculated=4550. The peroxide yieldis 24.3%.

EXAMPLE 12 Synthesis of diacyl-peroxide Having Structure (I) HavingY′=Cl EW=501

The equipment of Example 2 is used. 76.2 mmoles of NaOH dissolved in20.6 ml of water are introduced in the flask (200 ml). 60.79 mmoles ofH₂O₂ at 57.5% and 125 ml of a C₈F₁₈ are added to the solution. 50.36mmoles of perfluoroethereal acyl chloride having structure (I′) withY′=Cl having MW=547, are dropped in the reaction mixture in 15 seconds.The reaction exothermy is controlled so that the temperature rise in themixture does not exceed +11° C. The t_(max) is of 0.1 min. at 0° C. Theorganic phase is recovered as described in Example 1. The product is adiacylperoxide. The yield is 76%.

TABLE 1 Effect of the t_(max) on the diacyl peroxide yield of Example 1t_(max) Yield (min) % 0.1 45 3 65 8 50 12 35 20 25

What is claimed is:
 1. A process for obtaining (per)fluoroetheracylperoxides having an average equivalent weight (EW) in the range350-5000, having the formula:Y′—(CF₂—CF(CF₃)O)_(m)—(CX′FO)_(n)—CF₂CO—O—O—CO—CF₂—(OCX′F)_(n)—(OCF(CF₃)—CF₂)—Y′  (I)wherein Y′=Cl, OR_(f) wherein R_(f) is a C₁-C₃ perfluoroalkyl; m, n areintegers such that the average equivalent weight of (I) is in the rangeof 350-5000 and m/n≧40; X′=F, CF₃;T—CF₂—O—[(CF₂CF₂O)_(p)—(CF₂O)_(q)CF₂—CO—O—O—CO—CF₂(OCF₂)_(q)—(OCF₂CF₂)_(p)]_(y)—OCF₂—COOH  (II)wherein y is an integer comprised between 1 and 5; p and q are integerssuch as to give the above mentioned EW and p/q=0.5 to 2.0; T=COOH, Fwith the proviso that when T=COOH y=1-5, when T=F then y=1; startingfrom perfluoroether acylhalides having number average molecular weights(MV) in the range of 350-5000, having, respectively, the formula:Y′—(CF₂—-CF(CF₃)O)_(m)—(CX′FO)_(n)—CF₂CO—Y″  (I′) wherein Y′, X′, m andn have the meaning defined in (I); Y″=Cl, F;Y′″CF₂—O—(CF₂CF₂O)_(p)—(CF₂O)_(q)—CF₂—CO—Y″  (II′) wherein Y″ has themeaning defined in (I′); Y′″=CO—Y″, F; by reaction with H₂O in basicconditions at a temperature in the range −5° C. to 5° C. in a mixtureformed by two immiscible liquid phases having a total volume equal to atmost ⅔ of that of the reactor, kept under stirring so that no emulsionsare formed, said liquid phases being: an organic phase formed by(per)fluorinated solvents selected from C₆-C₁₀ linear chainperfluoroalkanes, perfluoropolyethers having perfluoroalkylic endgroups, optionally containing at one or both end groups a hydrogen atom,said perfluoropolyethers having a number average molecularweight in therange of 400-1000; an aqueous alkaline solution containing an excess ofhydrogen peroxide relative to the halide added; said process comprisingthe following steps: a) adding a (per)fluoropolyether monoacyl ordiacyl-halide, to a reactor having an internal volume in the range50-250 ml cooled with a 2 liter volume cryogenic bath having atemperature comprised between −40° C. and −80° C., so that the ΔTthermal rise is in the range 6° C. to 20° C., and such that when theaddition is complete the temperature decreases to the initialtemperature in a time period in the range of 0.1-5 minutes; b)conducting the ensuing reaction with stirring at the initialtemperature, for a time (t_(max)) to obtain the conversion of 75% of theacyl-halide of formula (I′) or (II′), said conversion determined byquantitative FTIR; and c) interrupting the reaction by stopping stirringand allowing the phases to be separated by maintaining the system at theinitial temperature, and subsequently recovering the organic phasecontaining the perfluoropolyether diacyl/polyacyl-peroxides.
 2. Theprocess according to claim 1 wherein in step a) the ratio between thealkali moles and the equivalents of —CO—Y″ functional groups is in therange 1.2-1.8 and the ratio between the aqueous phase ml volume and thebase grams is in the range 5-10 and the organic phase volume is halfthan that of the reactor.
 3. The process according to claim 1 wherein instep a), the reactant addition is preformed in a time ranging from 20 to30 seconds for (per)fluoropolyether acyihalides (I′) and (II′) having MWin the range 350-800 and the reaction time is less than or equal to 15seconds for (per)fluoropolyether acylhalides (I′) and (II′) having a MWin the range 800-5000.
 4. The process according to claim 1 wherein thesolvent is a perfluoropolyether.
 5. The process according to claim 1,which is continuous or batch.
 6. The process according to claim 1,wherein the (per)fluoroether acylperoxides are obtained having theformula (II) with equivalent weights (EW) in the range 1000-2000starting from (per)fluoropolyether acylhalides of formula (II′) with anumber average molecular weight in the range of 1000-2000.
 7. Theprocess according to claim 1 wherein (per)fluoropolyether acylperoxidesare obtained having the formula (I) with equivalent weight from 350 to800 starting from (per)fluoropolyether acylhalides of formula (I′)having number an average molecular weight in the range of 350-800. 8.The process according to claim 1 wherein in the reaction productsobtained starting from the (per)fluoroether acylhalides of formula (II′)the relative amounts of diacyl peroxides and polyacylperoxides are inrelation with the used hydrogen peroxide excess, and, the conditionsbeing the same, with the compound (II′) molecular weight.
 9. The processaccording to claim 1, wherein by using (per)fluoropolyether acylhalidesof formula (II′) having MW in the range 3000-5000, (per)fluoropolyetheracylperoxides of formula (II) wherein y=1 are obtained; and by using(per)fluoropolyether acylhalides number average molecular weights in therange 350-3000, polyacylperoxides mixtures are obtained and in formula(II) wherein y=1-5 and T=COOH.
 10. The (per)fluoropolyetheracylperoxides of formula (I) wherein Y′═Cl and the (per)fluoropolyetheracylperoxides of formula (II) of claim 1.